Acquired Immunodeficiency Syndome (AIDS), caused by the Human Immunodeficiency Virus (HIV), is a significant global public health issue. While effective therapeutics exist to treat AIDS patients, at present there is no cure. Furthermore, the HIV virus can rapidly develop resistance to existing treatments. Gag (group specific antigen) is a key structural protein of the HIV virion, comprising approximately 50% of the entire HIV virion mass. The roles of Gag in HIV viral maturation include driving assembly of the immature viral particle and packaging the viral RNA genome into the budding virion. To date, structural studies of Gag assembled into virus-like particles (VLPs) have been limited to lower resolution electron microscopy and biochemical studies. Magic angle spinning nuclear magnetic resonance (MAS NMR) is the optimal biophysical technique to characterize atomic-level, site-specific interactions of Gag, allowing for high-resolution studies of Gag at non- cryogenic temperatures, with no size or solubility restrictions. With MAS NMR, this research project will characterize structural and dynamic characteristics of Gag assembled into VLPs, as well as the protein's interactions with RNA. Preliminary results in all specific aims demonstrate that the proposed aims will be accomplished. Aim 1, resonance assignments and secondary structure determination of Gag assembled in VLPs, is a crucial first step in any NMR study of biomolecules and will address open questions regarding the secondary of structure of various domains of the protein. Research with respect to Aim 2 will characterize site-specific dynamics of the Gag polyprotein assembled into VLPs; quantifying timescales of dynamic processes in the protein will lend insight into the roles specific residues and regions of the protein play with respect to function. Characterization of atomic-level interactions of RNA with Gag assembled into VLPs, which are key given conformational changes that the polyprotein undergoes during viral maturation, will be accomplished in Aim 3. This research project addresses a critical gap in the understanding of HIV viral maturation and replication: the structural and dynamic features of Gag at the molecular level and the details of its interactions with the RNA viral genome. The insight gained from this research may be potentially important in the development of new therapeutics to treat AIDS.